Maximal Strength Effects of Cross Education Training on the Elbow Flexors

The purpose of this study was to compare the absolute and relative changes in maximal bilateral elbow flexion strength increase after a four-week intervention protocol between a unilateral and bilateral resistance training program in college age females. Methods: Five non-athlete females, with a mean age of 21.6 years, completed the study. Eligible subjects were randomly assigned to one of two groups; unilateral elbow flexion resistance training (n=2) or bilateral elbow flexion resistance training (n=3). Both groups completed a four-week resistance training three days per week using three sets of ten repetitions at 65% of their predicted one repetition maximum. Maximal strength increase was measured before and after intervention. The test arm (TA) was the untrained arm in the unilateral resistance training group (URT) and the designated arm in the bilateral resistance training group (BRT). The training arm in the unilateral group and the designated arm in the bilateral group were referred to as the control arm (CA). All subjects were permitted to continue regular exercise excluding any upper body exercises for the duration of the study. Results: Maximal elbow flexion strength increased by 16.7 ±11.8 pounds in CA and by 8.3 ±5.9 pounds in TA in the bilateral resistance training group. Comparatively, the unilateral resistance training group experienced a 17.5 ±12.4 pound increase in the CA in this group, and along with a 15 ±10.6 pound increase in strength in the TA. Percent crossover (PC) was calculated by dividing the change in pounds lifted by the TA by the change in pounds lifted by the CA and multiplying by 100. Compared to the control arm of unilateral resistance training protocol the percent cross over of the test arm was 85.71%. The percent cross over in the test arm in the bilateral resistance training group was 49.7%. There was no significant change in mid arm circumference or skin fold thickness from pre to post testing in either group. This eliminated the possibility of hypertrophy as this was a key aspect to the findings of neural mechanisms. Conclusion: In non-athlete, college age females unilateral resistance training caused a greater percent cross over in the test arm compared to the training arm, than bilateral resistance training following the same protocol. Both groups experienced bilateral maximal strength increases as previous studies have found. However, the magnitude of cross over demonstrated in the unilateral resistance training protocol was greater than previous studies that followed a similar protocol. In conclusion, this study found a greater percent cross over strength in the test arm following a unilateral resistance training protocol when compared to a bilateral resistance training protocol